Arrangement for disconnecting and removing series connected transformers from the circuit without causing disturbance



July 21, 1931. KUBLER 1,815,153

ARRANGEMENT FOR DISCONNECTING AND REMOVING SERIES CONNECTED TRANSFORMERSFROM THE CIRCUIT WITHOUT CAUSING DISTURBANCE Filed D80. 1, 1927 I fwg rto be effected in a Patented July 21, 1931 umrso STATES PATENT OFFICEBROWN, BOVERI AND CIE.,

OF BADEN, SWITZERLAND ARRANGEMENT FOR DISCONNECTING AND REMOVING SERIESCONNECTED TRANS- FORMER-S FROM THE CIRCUIT WITHOUT CAUSING DISTURBANCEApplication filed December 1, 1927,

be used, which have a contact track or are eonstructed in the manner ofchange-over switches. For operating the arrangement the same care mustbe observed as when using high tension apparatus, and the use ofautomatically acting devices is therefore difficult and expensive.

A more simple and suitable solution of the problem is obtained by usinga device which enables the preparatory switching operations low tensioncircuit, so that the switches lying in the high tension circuit can beof normal construction and be operated in a normal manner. The object ofthe present invention is to provide an arrangement for disconnecting andremoving series connected transformers from the circuit, in which on theseries transformer core, besides the primary winding and the secondarywinding which is in series with the network, there is a tertiary windingwhich is short-circuited by a resistance before the series connectedtransformer is disconnected, so that the disconnection of the primarywinding, followed by the direct bridging over of the secondary windingand before the disconnection and complete removal of the seriesconnected transformer from the circuit can be effected.

In the accompanying drawing a diagrammatic representation of thearrangement according to the invention is shown.

7 In this drawing 1 is the primary winding, 2 the secondary winding ofthe series connected transformer, 3 a tertiary winding which is on theiron core of the series con- Serial No. 237,091, and in Germany December3, 1926.

nected transformer and can be short-circuited through the resistance 4Lby means of the switch 5. 6 is the bridging switch for the secondarywinding 2 which may be completely cut out of the circuit by means of theknife switches 7 and 8. 9 is the switch for disconnecting the primarywinding from the network. The switch 9 and the knife switches 7 and 8are closed when under load, while the switches 5 and 6 are open.

The series connected transformer is disconnected and removed in thefollowing manner 1- First of all the switch 5 is closed and then theswitch 9 is opened. Thereupon the bridging switch 6 is closed and theknife switches 7 and 8 are opened. This disconnects the series connectedtransformer and entirely separates it from the network. The advantage ofthis arrangement as compared with those hitherto used resides in thefact that quite normal simple switches (not changeover switches) can beused. The number of turns of the tertiary winding is made such that thevoltage of the circuit of this winding is a low voltage. The switch 5and the resistance 4; can thus be made for low voltage and are thereforecheaper than is the case in the known methods. As the winding 3 and theresistance 4 are loaded only for a very short time, they may bedimensioned accordingly.

The series connected transformer will thus not be substantially largerthan hitherto in spite of its tertiary winding.

lVhether the primary winding of the series connected transformer isconnected directly to the network or whether this is effected by aseparate transformer, for instance a regulating transformer, isimmaterial as regards the provision and operation of the tertiarywinding on the series connected transformer. In this case it is alsounimportant whether the primary winding is disconnected by breaking theprimary circuit of the series or of the regulating transformer.

The resistance is preferably made with one step only but in specialcases a plurality of bridging resistances may be used in series or areslstance may be used which is adjustable or regulable in any suitablemanner. The size of the resistance is made such that the short-circuitvoltage trans mitted after short-circuiting the circuit of the tertiarywinding to the secondary winding will differ no more from the previoussecondary voltage than may be regarded as permissible in view of thedisturbance in the work of the network to be avoided.

lVhen in the three winding transformers of the figure the circuit of thewinding 3 is closed through the switch 5 over the resistance 4, withoutthe switch 9 being simultaneously opened, i. e. the primary winding 1being separated from the network, this does not constitute ashort-circuit of the transformer or of the network, as the resistance 4-limits the current of the winding 8 to a value corresponding to apermissible load. If in such a case the network feeding the winding 1has temporarily also an additional load, this does not in any wayconstitute a disturbance of the network operation. If the switch 9 isopened, then the current-carrying winding 2 has an exciting action onthe transformer, and in its turn generates a current in the winding 3,which current produces a flux that counteracts the flux of the winding2. The voltage, which then prevails at the terminals of the winding 2,is a function of the resistance 1 in the circuit of the winding 3,because this resistance is a part of the impedance of this circuit anddetermines that voltage at the terminals of the winding 3, which isrequired for driving the induced current through the resistance. If thewinding 2 is however bridged over by the bridging-over switch 6, thenboth winding 2, and the circuit of the winding 3 becomes currentless.The insertion of the bridging-over switch consequently also produces nodisturbance in the network of the winding 2, because no short-circuit ofa network supplying voltage is causcd thereby. The fact that then the o1ening of the switches 7 and 8 can take place without any disturbance, isclearly evident.

lVhat I claim is:

1. An arrangement for disconnecting and removing a series connectedtransformer from a circuit including primary and secondary transformerwindings, switch means connected with the primary winding, a network,switch means for connecting the secondary winding in series with the network, a bridging switch in the network for short circuiting thesecondary winding, a tertiary winding and resistance, and switch meansto short circuit the tertiary winding through the resistance.

2. An arrangement as claimed in claim 1, characterized by the featurethat the number of turns of the tertiary winding is made such that thevoltage of the circuit of this winding is a low voltage.

3. An arrangement as claimed in claim 1, characterized by the featurethat the ter tiary winding and the resistance connected up in itscircuit carry a comparatively large current as soon as the primarycircuit is open are loaded with high current density.

4:. An arrangement as claimed in claim 1, characterized by the featurethat the size of the resistance connected up in the circuit of thetertiary winding is made such that the induced voltage in the secondarywinding due to the current that flows in the tertiary winding circuitafter the tertiary winding circuit is closed will differ no more fromthe PIGXlOlIS secondary voltage than may be regarded as permissible inview of the disturbance in the work of the network to be avoided.

5. A method of removing a series connected transformer having a tertiarywinding in addition to the usual primary and secondary windings fromoperation in a network, which consists in first loading the tertiarywinding with a resistance, breakthe circuit of the primary winding,short circuiting the secondary winding and finally opening the secondarycircuit be tween the short circuiting points.

In. testimony whereof I have signed my name to this specification.

J OHANN ES KUBLER.

